The mystery of Pumice – floating rocks!

Most of us know rocks as being hard heavy objects that easily sink in water. The closest thing we see to rocks on top of water might be when we skip stones on a pond. But one rock, pumice, is so full of gas bubbles that it easily floats. And lately its been something I have been seeing amongst the seaweed and driftwood on my local beach (or at least my holiday beach in NSW, Australia).

White and light – pumice!

Pumice is a type of rock formed from the rapid cooling of volcanic lava that contains huge amounts of gas and steam. The gas and steam get ‘frozen’ into the cooled lava forming a lava froth. Under a microscope, pumice can be seen to be a frothy volcanic glass.

The pumice I am finding on the beach here came from a huge underwater eruption of the Havre Seamount that took place in June 2012. This volcano lies north-west of New Zealand, between New Zealand and Tonga. The eruption produce enough pumice to form a floating raft that was estimated to be 20,000 km2 (that’s HUGE – and bigger than some countries). The raft was dispersed by the tides, currents and winds and now the rock has been washed up on beaches along the South Pacific and Tasman Sea shores.

White pumice amongst the pebbles on a beach.

Pumice washing in the waves

While it’s a novelty for traveling rockhounds like me, ecologists have been concerned how these events may introduce invasive species of marine life as they hitch a ride on the floating rocks.

It floats! And it travels!

Pumice has many uses. It can be used a an abrasive – people buy pieces of it an beauty stores as a stone to rub off rough parts of their feet. It can be added to concrete mixtures as a light weight aggregate and the ancient Romans used pumice in their building aggregates. It’s even used to wash jeans – those stone-washed keepsakes! (See here for more information on the use of Pumice)

Pumice soils and farming
In some places on the planet people are farming on soil that is developed on pumice layers. In the central North Island of New Zealand for example, the pumice rich soils are used for growing commercial pines and dairy farms. The soils seem to hold water for plants, but can be nutrient poor.

As we head towards a warmer planet, it’s good to look back at past times and see what the Earth was like…and this time I head back 299 million years. Geologists call that period of Earth’s history the Permian.

Find the permian in this time scale…. it is after the Carboniferous and before the Triassic.

[The Earth’s history is broken up into geologic eons, era and periods. Go here to get a chart of the Earth’s history]

The Permian

The Permian period of time started around 299 million years ago when the Earth was in the deep freeze of an ice age. Most of the land on Earth was joined together into one huge continent that geologists call Pangea. Huge glaciers fed off massive ice sheets and moved towards the oceans. As they moved they ground up rock which was caught up in the ice. These glaciers reached the oceans and broke off chunks of ice that floated away from the continents as icebergs. When these icebergs melted, any rocks caught up in the ice dropped through the ocean and landed on the sea floor. Animals living on the ocean floor at this time had to survive the deluge of these ‘drop stones’. In some places, those animals with thick shells survived better than those with thin shells.

My budding little geologist sits on a Permian drop-stone at Wasp Head in Australia.

Evidence for the Permian period of time can be found in the rocks that made up the sea floor during the Permian. Layers of mud with drop stones and fossil animals with thick shells can be found around the world.

Drop stones

The remains os a bivalve mollusc…see how thick the shell material is? He needed to be strong to survive all the stone falling down from melting icebergs.

Over the next tens of millions of years (we are still in the Permian) the planet started to warm. The ice sheets and glaciers melted away from most of the globe. Then, after a few more tens of millions of years the ice ages returned and receded a few more times. So the Permian was a time of very varied climates…but overall it is considered to be a cold time in the history of the planet.

Permian – the catastrophic death of life

What is remarkable about the Permian…or at least the end of the Permian around 25o million years ago…is that something catastrophic happened to Earth. Exactly what happened is not really known – but it was so dramatic that 96% or more of sea life and 70% or more of land-dwelling life became extinct. It is the only know time on Earth in which most of the insects became extinct. For life on Earth, this catastrophic event was so major that it took the Earth over 10 million years to recover….and when it did it ushered in the world of the dinosaurs!

Scientists have put forward a number of possible causes for these mass extinctions during the end of the Permian. They include:

A. Earth being hit by a large meteorite or comet (that happened later in the history of the Earth and wiped out the dinosaurs). There is just a little evidence for this in the Permian – but being so old (250 million years ago) it is hard to find a definitive impact site etc.

B. A massive outpouring of basaltic lava. There are two places of Earth that are made up of vast amounts of lava that poured out during the end of the Permian. One place is the Siberian Traps where 2 million square kilometers was covered by lava right at the end of the Permian. The amount of volcanic gases and material released during these events could dramatically change Earth’s climate.

C. Methane hydrate release in the oceans. The Earth’s oceans contain vast amounts of ‘frozen’ methane gas found in an ice-like substance in sediments in the sea floor. Under the right conditions, these hydrates can be rleased in the ocean water, making the oceans toxic to life. The methane can also reach the atmosphere, changing climate.

D. Oceans anoxia – where the oceans lose most of their dissolved oxygen making if toxic for life. This may be triggered by massive amounts of carbon dioxide in the atmosphere – which in turn may be caused by huge volcanic eruptions (see above).

There are some other theories, including microbes and other gases. It may have been a combination of two or more of these things. Gathering scientific evidence and coming up with plausible explanations is the role of geologists who know (and love) rocks deposited in this time period.

Understanding these types of events can help us to understand the way our planet reacts to catastrophic changes as well as more subtle changes, either naturally occurring events (like increased volcanism) or human induced (like burning fossil fuels).

So the Permian was a time considerably different in climate as our own – but certainly was a time of some massive upheaval that shook life on Earth to it’s very foundations. For me, it provides a lesson to all of us that our planet is so very dynamic that we can expect change to occur even over the short lifespans of humans. How we be adapt to those changes is really up to us as a society.

I know this is not really about being a farmer…or about our struggles in trying to be one…but some things are just downright interesting and need to be talked about 🙂

If you like this kind of information you might also like the following:

I have learned some important life rules while I have trundled through my life. Many came from my Dad, and some others from mentors who took me under their wing. I think it’s a good set of rules to follow…along with what ever cultural or moral rules to which you want to adhere.

Maybe a mistake you would not want to make twice!

No doubt there are many little life rules that others follow to help them on the road to success – these are just mine. They have and continue to work well for me, and so I offer them for those looking for ideas on how to move forward…….

My seven life rules

Life Rules 1. It is ok to make a mistake…just don’t make the same mistake twice.This one is obvious…learn from your mistakes. It’s one I say to my staff as well as my colleagues when they despair about something not working as they planned.

Me and a group (and me hoping I am not the ‘one’)

Life Rules 2. There is one person in every group. Don’t be the one!
I run trips for groups of people, and have done for over 25 years. It is true that even with a small group there will be at least one person who requires “management” for some issue. Without the management, the issue can destroy their or the whole groups experience. So now I plan to have to deal with one person. But the real lesson is not to be that person that makes the rest of the group uncomfortable. Question your motive before any action that might cause disharmony.

Life Rules 3. Dress like you mean business and you will be treated like you mean business.
When I started work as a lowly staff member at one company, I was the only person who wore a tie every day. Not even the Executive Director did this. Then when a major meeting was called at a last minute with important clients, I was often pulled in as I looked “business”. This put me in the company of the higher management, and helped me to quickly rise through the ranks to become a Director of a group.
It’s a simple rule, and often discarded by people today who think it’s trendy to be an “individual” and not dress for business. The lesson here is that to dress for business is now the exception more than the rule, and so you stand out….and in today’s world you need to be able to stand apart from your peers for the right reasons.

Life Rules 4. First class people travel first class.
My Dad always said this…and while he may have meant it literally, he also meant to reflect on the importance of self esteem. If you feel that you are worthy to be treated well, then treat yourself well. Aspire to being first class it what ever you do, and you will be treated as first class by your peers and customers.
The flip side of this is if you are not worthy of being treated like top of your field, don’t try to act like you do, but rather strive to be “first class”.

Dress like you mean business…and stand next to large gold nuggets for extra effect!

Life Rules 5. Don’t hide your lamp under a bushel.Biblical origins, but quoted by my Dad to me a lot. If you have a skill or a talent, don’t hide it. Step up and sell it to your customers and clients. Those skills and talents are what makes you special and unique.

Life Rules 6. Don’t use a canon when a pea shooter will work.
When we strike problems in our lives people tend to react strongly and want to pull out a rapid and strong reaction. I am very guilty of this. So this rule is one I remind myself each and every time I have to deal with an “issue”. The question I ask is this: what is the minimum I can do to solve the problem? If that does not work, what is the next level of action and so on. I think that this approach has saved me from going into an issue “boots and all” only to find out that the issue was a smaller misunderstanding and then making me look foolish. This is a face-saver.

Life Rules 7. There are many ways to skin a cat!
This is sort of like the rule above (6) – it means that there are many solutions to a problem – not just the one in your mind. Sometimes this means that you have to ask others for ideas on solutions rather than just assume you way is the ONLY way. Having a few solutions can help you to keep rule 6 as well.